1. Field of the Invention
The invention concerns an electric machine with soft magnetic teeth at the air gap surface and a production process for such a machine.
2. Description of Prior Art
Electric machines with soft magnetic teeth at the air gap surface are known in a diversity of designs under the name of “step motor” or “switched reluctance machine”. The toothing causes the magnetic resistance of the magnetic flux, which flows through the air gap, to change as the rotor is moving. The utilizable forces depend on the tooth geometry, the magnetizability of the soft magnetic material, and the flux density in the air gap.
One design which is distinguished by its simple winding technique is the transversal flux machine. The soft magnetic body has gaps in circumferential direction that correspond to approximately one half of the pole width. The current flowing in the conductor ring can generate only a weak magnetic field in said gaps so that these circumferential sections contribute more to power loss than to useful performance.
From DE 43 25 740 C1, a transversal flux machine is known in which U-shaped soft magnetic cores are arranged around the conductor ring, the tangential width of said soft magnetic cores increasing disproportionately as the radius of the conductor ring increases. This results in gaps in circumferential direction between the radially inner ends of the cores which are wider than the width of the cores themselves.
In DE-OS 28 05 333 and DE 40 40 116 C2, segmented soft magnetic bodies are described in which the layering of the tooth cores is effected perpendicular to the layering of the yoke sheets.
From DE 34 14 312 A1, a permanent magnet excited machine with groups of electromagnets is known where the electromagnets have non-wound half-poles on both ends in direction of movement. The phase offset is generated by a gap between the electric pole units. The poles and half-poles have pole shoes which, with a plane air gap surface, provide only tight groove slots for inserting the wire winding. The ferromagnetic circuit of the electromagnet groups is made as a unit.
Furthermore, from DE 42 41 085 A1 is known the attachment of pole shoes to pole cores by means of dovetailing.
The objective of the present invention is, therefore, to advance a machine that is functioning in accordance with the reluctance principle in such a manner that, at reasonable production costs, the torque-to-bore volume ratio in relation to the air gap surface is increased and the ohmic and magnetic losses are decreased.